A two-component developing agent for use in a developing apparatus generally includes non-magnetic toner particles and magnetic carrier particles. In the developing apparatus, the toner particles and carrier particles are mixed, and the mixed particles are used as developing agent.
Such developing agent is applied to an electrostatic latent image formed on a surface of a photosensitive member to develop the electrostatic latent image as toner image.
Because the toner particles are consumed as the number of image forming times increases, a developing apparatus is supplied with fresh toner particles from a toner container via a toner refilling port of the developing apparatus. Such toner container maybe connected to the developing apparatus.
On one hand, the carrier particles are not consumed as the number of image forming times increases. However, the carrier particles need to be replaced with fresh carrier particles at a predetermined time because the carrier particles may degrade over the time.
Such replacement can be conducted by a service person by replacing used carrier particles with fresh carrier particles, or by replacing a cartridge-type developing apparatus including carrier particles therein, for example.
In one method, the carrier particles can be refilled in a developing apparatus by supplying fresh carrier particles from a refilling container to the developing apparatus, as required.
In another method, a refilling developing agent prepared by mixing carrier particles with toner particles in advance can be supplied to the developing apparatus, as, required.
In another method, excessive carrier particles can be ejected from a developing apparatus, as required, to prevent degradation of developing-agent.
In general, fresh toner particles or fresh carrier particles for refilling are supplied in the developing apparatus and are fed to a transport screw provided in the developing apparatus.
Then the fresh toner particles or fresh carrier particles are agitated with the developing agent existing in the developing apparatus by the transport screw, and transported to a developing roller.
If the developing agent is not effectively mixed with the fresh toner particles or fresh carrier particles in the developing apparatus, toner particles may not be effectively charged or may be charged with unfavorable polarity at the developing roller.
Such toner particles may scatter on a surface of a photosensitive member or in an image forming apparatus, which result into a degradation of image quality.
In view of such background, methods of refilling the developing agent to the developing apparatus have been studied. For example, a mixing effectiveness of developing agent can be improved by enhancing agitation effectiveness of particles.
In one method, agitation effectiveness is improved by providing an agitator for mixing fresh refilling particles and the developing agent and supplying such mixed particles to the developing apparatus. In another method, agitation effectiveness is improved by adjusting the height of the transport member such as screw with respect to a height level of developing agent in the developing apparatus.
In general, a transport screw mainly transports the developing agent in a shaft direction of the transport screw. Accordingly, the transport screw may not effectively mix fresh toner particles or carrier particles with the developing agent existing in the developing apparatus.
In case of refilling only the carrier particles, types of refilling particles can be reduced in number because the carrier particles can be commonly used for different color toners used for a color image forming apparatus. However, in such a case, effective agitation is required to mix the refilled carrier particles and the developing agent existing in the developing apparatus.
If the refilled carrier particles and the developing agent are not effectively mixed in the developing roller, toner particles may not be effectively charged or may be charged with unfavorable polarity at the developing roller.
Such toner particles may scatter on the surface of a photosensitive member or in an image forming apparatus, which result into a degradation of image quality.
However, excessive agitation may induce excessive energy to the developing agent. Such excessive energy may cause physical stress such as abrasion and break-up to the toner particles or carrier particles, and thus may degrade the developing agent.